[R] [External] Re: Parser For Line Number Tracing

[Duncan Murdoch]

And now I've found the elusive bug in show.error.locations = TRUE as 
well, and posted a patch for that too.

Back to the original topic of this thread:  I think most users should 
routinely use

  options(show.error.locations = TRUE)

e.g. in their .Rprofile.

That will often speed up bug fixes, especially if my patch is incorporated.

Duncan Murdoch



On 2025-01-20 5:56 p.m., Duncan Murdoch wrote:
> I've posted a patch to bugs.r-project.org that fixes the traceback()
> issue.  It's not specific to findFun3; you get the same problem with
> errors from expressions like
> 
>    1 + "a"
> 
> In my testing, I occasionally saw cases where show.error.locations =
> TRUE didn't work.  I'll try to track down a reproducible case, and
> perhaps a patch to fix it.
> 
> Duncan Murdoch
> 
> 
> 
> On 2025-01-20 9:37 a.m., Duncan Murdoch wrote:
>> Sorry, I'm not seeing the first problem now:
>> options(show.error.locations = TRUE) works fine.  Not sure what I did
>> wrong before.
>>
>> I'm still seeing `traceback()` failing to report the attempt to call
>> nofunction().  I suppose this is because a context is never set up for
>> the failed call.  Perhaps findFun3 could set up a fake context so that
>> traceback() adds one more entry?
>>
>> Duncan Murdoch
>>
>>
>> On 2025-01-19 3:39 p.m., Duncan Murdoch wrote:
>>> Thanks for pointing out the options.  Using
>>>
>>>        options(show.error.locations = TRUE)
>>>
>>> works on Ivo's example, but it doesn't show a location if the error
>>> happens in a function that doesn't have srcrefs, because the known
>>> location isn't on the top of the stack.
>>>
>>> Perhaps TRUE (and maybe "top"?) should look back through the stack until
>>> it finds a known location, and report that, or another option (e.g.
>>> "highest"?) could be added to do that.
>>>
>>> And still I think traceback() should show the top call in Ivo's example.
>>>
>>> Duncan
>>>
>>>
>>> On 2025-01-19 11:46 a.m., luke-tierney using uiowa.edu wrote:
>>>> On Sun, 19 Jan 2025, Ivo Welch wrote:
>>>>
>>>>> Hi Duncan — Wonderful.  Thank you.  Bug or no bug, I think it would be
>>>>> a huge improvement for user-friendliness if R printed the last line by
>>>>> default *every time* a script dies.  Most computer languages do so.
>>>>>
>>>>> Should I file it as a request for improvement to the R code
>>>>> development team?  Maybe R can be improved at a very low cost to the
>>>>> development team and a very high benefit to newbies.
>>>>
>>>> No. There are already many ways to influence the way the default error
>>>> handler prints information about errors, mstly via options(). In
>>>> particular you may want to look at entries in ?options for
>>>>
>>>> show.error.locations
>>>> showErrorCalls
>>>> showWarningCalls
>>>>
>>>> and adjust your options settings accordingly.
>>>>
>>>> Best,
>>>>
>>>> luke
>>>>
>>>>>
>>>>> Regards,
>>>>>
>>>>> /ivo
>>>>>
>>>>> On Sun, Jan 19, 2025 at 2:39 AM Duncan Murdoch <murdoch.duncan using gmail.com> wrote:
>>>>>>
>>>>>> On 2025-01-18 8:27 p.m., Ivo Welch wrote:
>>>>>>> I am afraid my errors are worse!  (so are my postings.  I should have
>>>>>>> given an example.)
>>>>>>>
>>>>>>> ```
>>>>>>> x <- 1
>>>>>>> y <- 2
>>>>>>> nofunction("something stupid I am doing!")
>>>>>>> z <- 4
>>>>>>> ```
>>>>>>>
>>>>>>> and
>>>>>>>
>>>>>>> ```
>>>>>>>> source("where-is-my-water.R")
>>>>>>> Error in nofunction("something stupid I am doing!") :
>>>>>>>        could not find function "nofunction"
>>>>>>> ```
>>>>>>>
>>>>>>> and no traceback is available.
>>>>>>
>>>>>> Okay, I see.  In that case traceback() doesn't report the line, but it
>>>>>> still is known internally.  You can see it using the following function:
>>>>>>
>>>>>> showKnownLocations <- function() {
>>>>>>        calls <- sys.calls()
>>>>>>        srcrefs <- sapply(calls, function(v) if (!is.null(srcref <- attr(v,
>>>>>>
>>>>>> "srcref"))) {
>>>>>>          srcfile <- attr(srcref, "srcfile")
>>>>>>          paste0(basename(srcfile$filename), "#", srcref[1L])
>>>>>>        } else ".")
>>>>>>        cat("Current call stack locations:\n")
>>>>>>        cat(srcrefs, sep = " ")
>>>>>>        cat("\n")
>>>>>> }
>>>>>>
>>>>>> I haven't done much testing on this, but I think it can be called
>>>>>> explicitly from any location if you want to know how you got there, or
>>>>>> you can set it as the error handler using
>>>>>>
>>>>>>        options(error = showKnownLocations)
>>>>>>
>>>>>> For example, try this script:
>>>>>>
>>>>>>        options(error = showKnownLocations)
>>>>>>        f <- function() showKnownLocations()
>>>>>>        x <- 1
>>>>>>        f()
>>>>>>        y <- 2
>>>>>>        nofunction("something stupid I am doing!")
>>>>>>        z <- 4
>>>>>>
>>>>>> I see this output from source("test.R"):
>>>>>>
>>>>>>       > source("test.R")
>>>>>>        Current call stack locations:
>>>>>>        . . . . test.R#4 test.R#2
>>>>>>        Error in nofunction("something stupid I am doing!") :
>>>>>>          could not find function "nofunction"
>>>>>>        Current call stack locations:
>>>>>>        . . . . test.R#6
>>>>>>
>>>>>> The first report is from the explicit call in f() on line 2 that was
>>>>>> invoked on line 4, and the second report happens during error handling.
>>>>>>
>>>>>> I supppose the fact that traceback() isn't showing you the line 6
>>>>>> location could be considered a bug.
>>>>>>
>>>>>> Duncan Murdoch
>>>>>>
>>>>>>
>>>>>
>>>>> ______________________________________________
>>>>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>> PLEASE do read the posting guide https://www.r-project.org/posting-guide.html
>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>>
>>>>
>>>
>>
>